The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In a vehicle equipped with a DCT, engine torque is transferred to drive wheels via gear shifting utilizing two clutches. The two clutches are connected to respective input shafts within the DCT so as to realize shift stages assigned to the respective input shafts. The shift stages assigned to the two input shafts are generally divided into odd-numbered stages and even-numbered stages such that any one input shaft may realize only odd-numbered stages and the other input shaft may realize only even-numbered stages.
Power-on upshift is shifting to a higher shift stage among a series of shift stages in the state in which a driver depresses an accelerator pedal. In the case of a DCT, upshifting during traveling is shifting from an N stage, which is a shift stage assigned to one input shaft, to an N+1 stage, which is a shift stage assigned to the other input shaft.
At this time, a clutch, which is connected to the input shaft realizing the N stage as a current shift stage, is disengaged, and reduced engine torque must be input thereto. A clutch, which is connected to the input shaft realizing the N+1 stage as a target shift stage, is engaged, and increased engine torque must be input thereto.
Upon shifting, the clutch, which is disengaged for the input of reduced engine torque thereto, is referred to as a “disengaging clutch”, and the input shaft connected thereto is referred to as a “disengaging input shaft”. The clutch, which is engaged for the input of increased engine torque thereto, is referred to as an “engaging clutch”, and the input shaft connected thereto is referred to as an “engaging input shaft” or a “target shift-stage input shaft”.
When the driver depresses the accelerator pedal during power-on upshifting, the engine torque increases in response to a driver accelerator pedal depression amount. At this time, if an engaging clutch torque does not increase as the engine torque increases, a flare phenomenon may occur. The flare phenomenon occurs when the increase in the engaging clutch torque does not match with the increase in the engine torque and thus an engine speed is not synchronized with a target shift-stage input shaft speed. Therefore, control is performed to increase the engaging clutch torque in response to an increase in engine torque.
However, we have discovered that the control of simply increasing the engaging clutch torque in response to an increase in engine torque causes excessive change to engine angular acceleration so that shocks at the end of shifting occurs.
Details described as the background art are intended merely for the purpose of promoting the understanding of the background of the present disclosure and should not be construed as an acknowledgment of the prior art that is not known to those of ordinary skill in the art.